Rectal Administration of Nifedipine: Haemodynamic Effects and Pharmacokinetics in Hypertensives

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Abstract
The haemodynamic effects and pharmacokinetics of nifedipine suppositories, used mainly for hypertensive emergencies, were studied in 10 severely hypertensive patients. Following rectal administration, significant hypotensive effects occurred after 0.5 h and lasted until 7 h after administration. The mean (±SE) maximum decreases in systolic and diastolic blood pressures 1.5 h after administration were: systolic, 61.8 ± 7.9 mmHg ( P<0.001); and diastolic, 30.8 ± 4.0 mmHg (P<0.001). No serious side-effects were reported and heart rate did not change significantly. Mean nifedipine concentration in the blood peaked at 52.4 ng/ml, 1 h after administration and, after 7 h, was still 14.3 ng/ml which is higher than the minimum plasma concentration required for hypotensive effects to occur. There was a close correlation between nifedipine concentration in the blood and hypotensive effects. These results indicate that rectal administration of nifedipine should be regarded as a useful alternative treatment in hypertensive emergencies.